It is known in the art to employ various types of discharge lamps for sterilising objects or for reducing the number of living organisms in, for example, the packing of medical care instruments and utensils, or in the aseptic packing of foods. Such discharge lamps can, for example, in a uniform or pulsating flow, radiate UV light. In addition to light, such lamps generate heat which must be led off to prevent the lamps from deteriorating such that they give lower light efficiency or have shorter service life. This problem is normally solved by means of liquid cooling, i.e. a liquid--normally water--is caused to flow along the luminant parts of the lamp in order to cool them and keep the lamp at an acceptable working temperature. A particular problem in this context is discharge lamps of the type which include a curved, for instance U-shaped, luminant body. While such a configuration makes it possible, for example, to irradiate a partly finished packaging container interiorly, the U-shape of the luminant body gives a manifest thermal concentration at the curved section of the luminant body, which implies that this will operate at a relatively high working temperature even if the lamp is provided with liquid cooling. Conventional liquid cooling of this type of discharge lamp utilises a liquid container or envelope of, for example, quartz glass in which the luminant body is placed. Inflowing coolant is led by the intermediary of, for example, an insert along the luminant body so that the liquid flows along the one shank of the body, past the curved section and returns along the opposing shank of the luminant body. Since the temperature of the cooling water is at its lowest when it flows into the liquid container, this construction results in the one shank of the luminant body (more precisely at its starting end) having the most powerful cooling effect, while the cooling water will have been heated somewhat already on arrival at the curved section of the luminant body so that cooling of this section is not optimal.
There is thus a general need in the art to provide a liquid-cooled discharge lamp of the type which includes a curved or U-shaped luminant body, the discharge lamp having a cooling system adapted to the configuration of the luminant body which ensures that maximum cooling is obtained at the warmest site of the luminant body.